[SOLVED] 'enum class' with QVariant (How to register strongly typed enum with Qt Meta System?)
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Solution: Registration of mata-type was not an issue. QVariant does not have constructor taking a template value. In order to use it with custom types from Qt Meta System QVariant::seValue must be used.
Hi,
I have been searching but nothing I found worked for me (using Qt 5.3beta) so I figured to ask a new question.
How to register strongly typed enum with Qt Meta System?
I have:
@
class MyEnums : public QObject
{
//Q_ENUMS(Enum)
public:
enum class Enum : int
{
A,
B,
C
};
};Q_DECLARE_METATYPE(MyEnums::Enum)
@and then elsewhere
@
void Class::foo()
{
QVariant var(MyEnums::Enum::A);
}
@which gives me compile error.
Using
@
qRegisterMetaType("MyEnums::Enum");
@also does not work and it tells me the type is not registered and I should use Q_DECLARE_METATYPE macro which I clearly did though...
Switching to regular enum (i.e. 'enum' instead of 'enum class') works however.
Also I will require to register the enum with Q_ENUMS as well (as indicated in the first snippet). I am pointing it out in case it could be the problem too.
Thanks for help!
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Hi, it works fine with "enum class" and Q_DECLARE_METATYPE in my app, I have also used Q_ENUMS but I think that is only necessary because I use the enum values in QML.
Is it working if your remove the int type?
I mean
@
enum class Enum // : int
@
I did not change the type, but I thought "int" is the default type anyway so it should be exactly the same code if you write " : int" or omit it? -
Oh I was so dumb... I did not notice that no constructor of QVariant is taking template type. In order to use it with custom types registered QVariant::setValue has to be used instead.
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Oh sorry I noticed that befre but thought it would also work, I guess you can't use the QVariant constructor for custom types, so replace
@
QVariant var(MyEnums::Enum::A);
@
with
@
QVariant var = QVariant::fromValue(MyEnums::Enum::A);
@
and it should work :)Edit: haha you changed your post while I was compiling your project, anyway you can use the static function QVariant::fromValue instead of setValue, so this post is not entirely useless i guess. :D
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Sorry for changing my post, I figured it was redundant given such a
simplemistake.And thanks a lot for your help! Incidentally that static function you pointed out is actually more useful to me than setValue. :-)